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Cell life cycle (including Mitosis)
Cell life cycle (including Mitosis)
Pg. 151-159Pg. 151-159
All cells pass through a series of events called the cell cycle.
Some cells cycle continually (skin, root tips), other cell types only a limited number of times before they stop multiplying (brain, nervous, etc.) and eventually die.
The cell cycle is divided into several stages.
All cells pass through a series of events called the cell cycle.
Some cells cycle continually (skin, root tips), other cell types only a limited number of times before they stop multiplying (brain, nervous, etc.) and eventually die.
The cell cycle is divided into several stages.
Interphase Interphase Most of cell cycle (95%) = normal cell
functioning Cell increases in size Organelles replicate. DNA replicates. Readies for mitosis DNA condenses Three parts:
G1 = Cell growth; Normal cell functions
S = DNA replicatedG2 = DNA condenses into chromosomes
Strands = sister chromatids2 Chromatids connected by centromere
Most of cell cycle (95%) = normal cell functioning
Cell increases in size Organelles replicate. DNA replicates. Readies for mitosis DNA condenses Three parts:
G1 = Cell growth; Normal cell functions
S = DNA replicatedG2 = DNA condenses into chromosomes
Strands = sister chromatids2 Chromatids connected by centromere
ChromosomesChromosomes The organelle into
which DNA is packaged
Contains proteins called histones – which give DNA support
Chromatin is what DNA is called when it is not tightly coiled during cell division
Chromosomes only “appear when a cell is dividing”
The organelle into which DNA is packaged
Contains proteins called histones – which give DNA support
Chromatin is what DNA is called when it is not tightly coiled during cell division
Chromosomes only “appear when a cell is dividing”
Why divide? Why not increase in size?Why divide? Why not increase in size?
As organisms grow, the size of their cells do not increase they simply divide into more cells!
Cells need a high surface area to volume ratioREMEMBER: Cell membrane lets things in (like
glucose) and removes others (carbon dioxide) Very large cells cannot let things in and out fast
enough to maintain the needs of the larger cell
ANSWER: Cells divide after growth or die because eventually they cannot sustain the needs of their internal environments
As organisms grow, the size of their cells do not increase they simply divide into more cells!
Cells need a high surface area to volume ratioREMEMBER: Cell membrane lets things in (like
glucose) and removes others (carbon dioxide) Very large cells cannot let things in and out fast
enough to maintain the needs of the larger cell
ANSWER: Cells divide after growth or die because eventually they cannot sustain the needs of their internal environments
MitosisMitosisThe multi-
step process of cell division in the cell cycle is called mitosis.
The multi-step process of cell division in the cell cycle is called mitosis.
What is the purpose of Mitosis?What is the purpose of Mitosis?
1. Maintain a high surface area to volume ratio when cells grow.
2. Reproduction (When unicellular organisms go through mitosis there are now two identical organisms.)
3. Multicellular organisms go through mitosis to:
1. produce new cells to grow (bone cells)
2. replace damaged or dying cells (blood cells)
1. Maintain a high surface area to volume ratio when cells grow.
2. Reproduction (When unicellular organisms go through mitosis there are now two identical organisms.)
3. Multicellular organisms go through mitosis to:
1. produce new cells to grow (bone cells)
2. replace damaged or dying cells (blood cells)
Mitosis overviewMitosis overviewProduces two identical cellsEach cell has a full set of
DNA (diploid – two sets for each gene)
Stages of Mitosis:ProphaseMetaphaseAnaphaseTelophase
Produces two identical cellsEach cell has a full set of
DNA (diploid – two sets for each gene)
Stages of Mitosis:ProphaseMetaphaseAnaphaseTelophase
Which cells are undergoing mitosis?
Prophase (early)Prophase (early)Chromosomes shorten and thickenNuclear membrane disappears
Chromosomes shorten and thickenNuclear membrane disappears
Prophase (late)Prophase (late) Spindle fibers formed from microtubules Microtubules surround centromere Chromosomes begin to move
Spindle fibers formed from microtubules Microtubules surround centromere Chromosomes begin to move
MetaphaseMetaphasePairs of sister chromatids align at
center (middle/metaphase)Forms metaphase plate
Pairs of sister chromatids align at center (middle/metaphase)Forms metaphase plate
AnaphaseAnaphaseChromatids separate at centromereChromatids pulled apart in opposite
directions toward polesEqually divides DNA
Chromatids separate at centromereChromatids pulled apart in opposite
directions toward polesEqually divides DNA
TelophaseTelophaseCell cytoplasm readied for divisionSpindle fibers disassemble2 Nuclear envelopes reformCytokinesis occurs
Cell cytoplasm readied for divisionSpindle fibers disassemble2 Nuclear envelopes reformCytokinesis occurs
Cytokinesis (part of telophase)Cytokinesis (part of telophase)
Division of cytoplasm and organelles to create 2 new identical cells.
--Includes the construction of cell membrane between two new cells
--Process differs in animals and plant cells
Division of cytoplasm and organelles to create 2 new identical cells.
--Includes the construction of cell membrane between two new cells
--Process differs in animals and plant cells
AnimalAnimalCell pinched in twoPinching at cleavage
furrow
Cell pinched in twoPinching at cleavage
furrow
• New cell wall must be laid down• Cell plate forms
Plant